Regarding the issue of the relative height of the arrangement in thermal siphon reboilers

What does 2-1-3 mean?

Thank you for the explanation, but I still don’t understand the issue regarding the relative position to the tower – whether it’s too high or too low

Calculate the pressure drop of the fluid in the column to the reboiler outlet by comparing power and pressure drop. Both too high and too low reboiler temperatures will degrade heat transfer efficiency. It generally does not get too high, as the outlet of the reboiler is directly connected to the tower.

I understand that the power requirement for a reboiler at lower temperatures should be higher

Firstly, thermal siphon reboilers are generally vertical types; horizontal thermal siphon reboilers are used very rarely, as they are relatively less efficient and more difficult to control. It is also important to understand the issue of the installation height of thermal siphon reboilers. It is recommended to read about a dozen articles first to grasp the basic principles before asking about more detailed aspects. In terms of the design of shell-and-tube heat exchangers, I believe that calculating vertical thermal siphon reboilers is quite difficult, mainly because it’s hard to determine the appropriate installation height. There are many factors that affect this installation height, and these need to be taken into consideration during the design process. However, vertical thermal siphon reboilers represent the option with the lowest investment cost

This requires detailed calculations; if we consider the impact based on approximate positions, an excessively high value makes it difficult to control the liquid level inside the reboiler, leading to excessively high local temperatures in the reboiler, which can pose a risk. At the position shown in Figure 3, either the reboiler does not have a sufficient liquid level, or when the reboiler is filled with liquid, the liquid in the tower may already submerge the thermal siphon outlet, making it difficult to establish a circulation. The gas generated by heating the reboiler cannot be discharged in time and tends to accumulate inside the siphon tube. If it is too low, the siphon tube may be filled entirely with liquid, making it difficult to establish circulation. Of course, the design of the reboiler also has an impact. I’m also looking forward to the expert’s answer for the calculation:D

Too much power is also not acceptable; some design documents recommend adding a valve to the inlet pipeline for regulation. Below the reboiler is the liquid phase, followed by a gas-liquid mixture. The driving force for the reboiler comes from the decrease in density resulting from the vaporization of the liquid phase; if this position is too low, the driving force becomes excessive, the proportion of liquid phase increases, and the heat exchange efficiency declines as well

I’m an amateur:( I didn’t understand it